1. Field of the Invention
The present invention relates to an input device used for operating various electronic apparatuses.
2. Background Art
Electronic apparatuses such as mobile phones and music players have become more functional and more compact in recent years. In line with this trend, there is a growing demand for input devices that perform diverse operations in electronic apparatuses. One such conventional input device will be described as follows with reference to FIGS. 8 and 9.
FIG. 8 is a sectional view of conventional input device 15. FIG. 9 is an exploded perspective view of electronic apparatus 20 using input device 15. In these drawings, the dimensions of some parts are exaggerated to facilitate understanding. Electronic apparatus 20 includes input device 15, upper casing 16, lower casing 17, and panel sheet 18.
Input device 15 includes touch panel 6, display element 7, damper sheet 8, and wiring board 9. Touch panel 6 is a capacitance type. Display element 7 can be a liquid crystal display element. Damper sheet 8 can be made of rubber. Wiring board 9 is provided on its upper and lower surfaces with wiring patterns (not shown). Display element 7 and touch panel 6 are stacked in that order on the top surface of wiring board 9 via damper sheet 8.
Touch panel 6 includes upper surface cover 1, upper substrate 2, and lower substrate 3, all of which are made of light-transmissive glass or light-transmissive resin. Touch panel 6 further includes upper electrodes 4 on the top surface of upper substrate 2. Upper electrodes 4 are belt-shaped and made of a light-transmissive material such as indium tin oxide. Upper substrate 2 is bonded to upper surface cover 1 via an adhesive (not shown) applied to the top surface of upper substrate 2 and/or the top surface of upper electrodes 4.
Touch panel 6 further includes lower electrodes 5 on the top surface of lower substrate 3 so as to be at right angles with respect to upper electrodes 4. Lower electrodes 5 are also belt-shaped and made of a light-transmissive material such as indium tin oxide. Lower substrate 3 is bonded to the bottom surface of upper substrate 2 via an adhesive (not shown) applied to the top surface of lower substrate 3 and/or the top surface of lower electrodes 5.
Input device 15 further includes controller 10, detecting circuit 11, driving circuit 12, and connector 13 on the top surface of wiring board 9. Controller 10 is a semiconductor device such as a microcomputer. Detecting circuit 11 and driving circuit 12 are formed of electronic components such as resistors and diodes, and are connected to controller 10 via wiring patterns.
In input device 15, upper and lower electrodes 4 and 5 of touch panel 6 and display element 7 are electrically connected to controller 10, detecting circuit 11, and driving circuit 12 via connector 13, film-like flexible wiring board 14 having wiring patterns, and other components.
Upper and lower casings 10 and 17 are made of insulating resin, each of which is shaped like, a box. Film-like panel sheet 18 is pasted on the top surface of upper casing 16. Touch panel 6, display element 7, and wiring board 9 connected to other electronic components and batteries (not shown) are housed between upper casing 16 and lower casing 17 in electronic apparatus 20.
Assume that a menu (not shown) including icons is displayed on display element 7 on the rear surface of touch panel 3 and that a user places a finger on the portion of the top surface of upper surface cover 1 that is on a desired icon. Then, part of the electric fields discharged from upper and lower electrodes 4 and 5 connected to driving circuit 12 is absorbed into the finger.
This results in changes in the electric field. The changes are detected by detecting circuit 11 connected to upper and lower electrodes 4 and 5. Controller 10 detects the finger contact position from the detection result of detecting circuit 11, and then selects the icon desired by the user. Display element 7 displays the application for the selected icon.
If it is desired to detect that the user brings a finger close to the top surface of upper surface cover 1, driving circuit 12 can be made to generate a larger electric field. In this case, the electric field is discharged far beyond the top surface of upper surface cover 1, allowing detecting circuit 11 to detect changes in the electric field due to the approach of the finger.
Thus, in the conventional input device, detecting circuit 11 detects changes in the electric field generated by driving circuit 12, and then controller 10 detects the position on which the user places a finger, or toward which the user moves a finger.
In the conventional input device, however, the user may fail to locate the exact position when the menus and keys are small compared with the size of his/her finger. This makes it difficult for input device 40 to perform diverse operations. Such an inconvenience occurs when the user selects a desired menu or key on display element 7 including a number of menus and a small QWERTY keyboard.